The relationship between cellular metabolite levels and neuronal transmission is being investigated in hippocampal preparations in vitro. The concentrations of the adenylates, phosphocreatine, creatine, lactate, and the cyclic nucleotides are evaluated for slices during in vitro incubations of up to 8 hours, and during transient periods of anoxia and ischemia. The magnitude of the evoked field potential is also recorded. The rate and degree of metabolic recovery following decapitation appear to be dependent on slice thickness, but not on the presence of glucose and oxygen during the initial preparation period. In addition, creatine and cyclocreatine are being tested for their dose and time-dependent effects on high energy phosphates and duration of transmission during anoxia. Added creatine results in the elevation of phosphocreatine concentrations, while cyclocreatine presumably causes an accumulation of cyclocreatine phosphate. ATP levels are unaffected by added creatine, and decreased by cyclocreatine. Both compounds prolong transmission when present in concentrations from 5 to 25 mM, though cyclocreatine also appears to act as a convulsant.